The golden langur, Trachypithecus geei, is an endangered species endemic to India and Bhutan. Its distribution is limited to a small forest belt in western Assam in Northeast India and Bhutan, between the River Manas in the east, River Sankosh in the west and the Brahmaputra in the south. Chakrashila Wildlife Sanctuary straddling Kokrajhar and Dhubri districts of Assam is the only protected habitat for the golden langur in India. From December 2006 to January 2007, we carried out the first survey of the golden langur in the sanctuary. Data were collected using line transects and total counts. We counted 474 individuals in 64 troops in and around the sanctuary through direct sightings. Group size ranged from 3 to 15 individuals, with a mean size of 7.4. The adult sex ratio was 1:1.53, and the ratio of adult females to infants was 1:0.617. The age structure of the population counted comprised 49.8% adults, 33.5% juveniles and 16.7% infants. Domestic dogs (Canis familiaris) and illegal felling were found to be the major threats for golden langur in this protected habitat. We hope that this report will help guide future conservation efforts for the golden langur and for the management of the Chakrashila Wildlife Sanctuary.